Advice please - application of AS2970

Alij78

Hi there, newbie here!
We purchased a block of land in April this year, it had been part of a subdivision of one block into 3. As part of the subdivision a proposed building envelope had been submitted to court based on the location of several (8) large trees - the subdiision was granted for approval by L&E court late 07/early 08. So we purchase this year and go about designing a house, because of the trees we used an arborist to tell us the areas we could use etc. The arborist we used had numbers for the CRZ and TPZ the same as another arborist who had done the report for the initial subdivision.
So (sorry so long) we then submit plans to council and for this particular tree a Bangalay 15m high with DBH 400mm and canopy spread of 5m, we sit a 5m long wall of the house 3.1m away. The 5m stretch of wall then has a 5.5 alfresco area so all up a 10.5 m stretch of slab. The 2 arborists had a critical root zone of 3.5m and protected root zone of 7m. There is nothing being built on any other sides of the tree. The council is saying we have to be 5m away based on the new AS2970.
What is valid here? The court granted this block based on a building envelope that took into account the CRZ based on the standards that applied at that time, we designed our house based on those same standards as applied at the time, in heavy consultation with arborist and council, and now they are saying a whole new standard will apply which basically means a complete redesign of our house, and leaves only about 30% of our land usuable (we have been told there is no way the courts would have approved the block on these new numbers as it is just not reasonable)
I should add we want to retain this tree and thought we were doing the right thing!
Any advice greatly appreciated!!!!
Thanks in advance

Alij78

oops sorry, typo - meant to say:

The 2 arborists had a critical root zone of 2.0m and protected root zone of 4.0m.

Thanks so much!

Eric Frei

I think you mean AS 4970 which only came out August this year.

AS 4970 uses 12 x DBH as a TPZ and the formula for SRZ is cumbersome but there is a chart you can use.

Encroachment greater than 10% into the TPZ has to be justified with reasoning. You have to demonstrate that the tree will not decline somehow.

Being a euc it will get tougher than other species to push that 10% further.

You have been caught between what was arborist opinion prior to Aug 2009 and a standard there-after. Not a lot you can do but perhaps go back to court with an application for some tree removals and see what happens.

On a recent urban house block site I was on the tree had a 1m DBH therefore required (at 12 x DBH) 452m2 of land as a TPZ, when a generous house block is 700m2 these days you can see the absurdity of it all. Sometimes location of the tree regardless of health warrants removal so people can build their home .... that is your argument and don't ever forget it.

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Sean Freeman

Hello Alij78,

I would advise you to consult with an urban planner, it sounds like your application has been caught up in the often complicated workings of the local planning scheme and other state and (possibly) federal legislation.

It can be very messy, conflicts that can arise between the person wanting to develop a lot and the rules of the local planning scheme are not simple to resolve and certainly can't be done on an internet forum.

Alij78

thanks so much for your response guys! have ended up purchasing the standard myself and done the calculations and looks like on the current house we propose we will encroach in the TPZ by 12.1%!!!

If we move the house 380mm away we will be under the 10 though, which we can live with and should meet the AS 4970 requirements as there is nothing on any of the other 3 sides of the tree so the TPZ can be compensated plus if we use the recommendations by our initial arborist for construction and protection of the tree, should be ok!

(I think????)

Anyway, thanks so much again!

PS. If anyone feels a side comment, would appreciate your advice - our initial arborist report was done in August but made no mention of the new standards despite knowing it was for a DA that was to be submitted post 29 August 2009 implementation of the new standards - we were a little disappointed that he didn't mention the new calculations to us nor in the report at all - is this reasonable? thanks again

Eric Frei

Well, likely he didn't know that's all.

You can encroach more than 10% anyway, just have to have sound reasoning and care for the tree.

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Alij78

Thanks for the quick reply!!!

OK I understand re the new standard, I thought it might have had advanced warning re its implementation or something along those lines

Council are being very picky with this tree so I think if we can live with cutting a little off our house and being under the 10% then that is a pretty strong argument (I hope??!!???)

Eric Frei

I'd say so.

They'll still want to see a Tree Protection plan, you have to detail how the tree will be managed.

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